The primary objectives of this proposed research are to synthesize some unique cap structures and to attach them to Poly (U) messenger RNA with 3'-Poly (A) end of varying lengths. The modification in the structure will be the addition of spin label derivative to the cap structure and the addition of photoaffinity labels such as azido and thio groups and fluorescamine fluorescen probe attached to the amino group of guanine and adenine bases in the cap structure. We will use the technique of Electron Paramagnetic Resonance (EPR) to monitor the behavior of spin labels and we will use a wheat germ system to monitor the influence of the modification of photoaffinity label and fluorescent probe on the translation efficiency of the synthetic messenger modified specifically at the cap structure and at the 3'-Poly (A) end. In addition, we plan to obtain commercially prepared rabbit-9S-globin messenger RNA and use capping and decapping enzymes to modify its 5'-terminal structure. We will then add back the cap structure modified in several ways: a) cap structure containing a spin label probe; b) cap structure containing a fluorescent probe; and c) cap structure containing a photoaffinity label probe. We will prepare hybridizable cap structure analogs. For example one type of cap structure that has been identified is the following: 7-methyl-C5' ppp5'C2'O methyl pCp. We will prepare the analogous hybridizing sequence, 4-methyl-C5' pp5'C2'O methyl pCp and sequences containing less nucleotide than the entire structure, for example, 4-methyl-C5' ppp5'C.